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(os occipitale), unpaired, participates in the formation of the posterior part of the base and vault of the skull (Fig. 1). It distinguishes between the basilar part, 2 lateral parts and scales. All these parts, connecting, limit large hole (foramen magnum).
Rice. 1.
a - topography of the occipital bone;
6 - outside view: 1 - external occipital protuberance; 2 - the highest nuchal line; 3 - upper nuchal line; 4 - lower nuchal line; 5 - condylar canal; 6 - occipital condyle; 7 - intracranial process; 8 - the basilar part of the occipital bone; 9 - pharyngeal tubercle; 10 - lateral part of the occipital bone; 11 - jugular notch; 12 - jugular process; 13 - condylar fossa; 14 - large hole; 15 - external occipital crest; 16 - occipital scales;
c - inside view: 1 - groove of the superior sagittal sinus; 2 - internal occipital protuberance; 3 - internal occipital crest; 4 - large hole; 5 - sigmoid sinus groove; 6 - furrow of the lower stony sinus; 7 - slope; 8 - the basilar part of the occipital bone; 9 - the lateral part of the occipital bone; 10 - jugular tubercle; 11 - jugular process; 12 - cruciform eminence; 13 - groove of the transverse sinus; 14 - scales of the occipital bone;
d - side view: 1 - lateral part of the occipital bone; 2 - slope; 3 - basilar part of the occipital bone; 4 - furrow of the lower stony sinus; 5 - pharyngeal tubercle; 6 - the canal of the hypoglossal nerve; 7 - jugular process; 8 - occipital condyle; 9 - condylar canal; 10 - condylar fossa; 11 - large hole; 12 - occipital scales; 13 - lambdoid edge of the occipital scales; 14 - mastoid edge of the occipital scales
Basilar part(pars basilaris) in front fuses with the body of the sphenoid bone (up to 18-20 years of age, they are connected by cartilage, which subsequently ossifies). In the middle of the lower surface of the basilar part there is pharyngeal tubercle (tuberculum pharyngeum), to which the initial part of the pharynx is attached. The upper surface of the basilar part faces the cranial cavity, is concave in the form of a groove, and together with the body of the sphenoid bone forms a clivus. The medulla oblongata, bridge, vessels and nerves are adjacent to the slope. On the lateral edges of the basilar part there is sulcus of the lower stony sinus (sulcus sinus petrosi inferioris)- the place of attachment of the venous sinus of the same name of the dura mater.
Lateral part(pars lateralis) connects the basilar part with the scales and limits a large opening from the lateral side. On the lateral edge there is jugular notch (incisura jugularis), which, with the corresponding notch of the temporal bone, limits the jugular foramen. Along the edge of the clipping is intracranial process (processus intrajugularis); it divides the jugular foramen into anterior and posterior parts. In the anterior section is the internal jugular vein, in the posterior - IX-XI pairs of cranial nerves. The posterior part of the jugular notch is limited by the base jugular process (processus jugularis), which faces the cranial cavity. On the inner surface of the lateral part, posteriorly and medially from the jugular process, there is a deep sulcus sinus sulcus (sulcus sinus sigmoidei)... In the anterior part of the lateral part, on the border with the basilar part, it is located jugular tubercle, tuberculum jugulare, and on the lower surface - occipital condyle (condylus occipitalis), which connects the skull to the 1st cervical vertebra. Behind each condyle is condylar fossa (fossa condylaris), at its bottom there is an opening of the emissary vein (condylar canal). The base of the condyle is pierced canal of the hypoglossal nerve (canalis nervi hypo-glossi) through which the corresponding nerve passes.
Occipital scales(squama occipitalis) has an upper lambdoideus (margo lambdoideus) and bottom mastoid margin (margo mastoideus). Outside surface scales are convex, in its middle there is external occipital protuberance (protuberantia occipitalis externa)... Down towards the big hole, it continues into external occipital crest (crista occipitalis externa)... Perpendicular to the ridge, the upper and lower nuchal lines (lineae nuchalis superior et inferior)... Sometimes the highest nuchal line (linea nuchalis suprema) is also noted. Muscles and ligaments are attached to these lines.
Inner surface occipital scales concave, has an internal occipital protuberance in the center (protuberantia occipitalis interna), which is the center cruciform eminence (eminentia cruciformis)... Upward from the internal occipital protuberance departs sulcus of the superior sagittal sinus (sulcus sinus sagittalis superioris), downwards - the internal occipital crest (crista occipitalis interna), and to the right and left - sulci sinui transversi.
Ossification: at the beginning of the 3rd month of intrauterine development, 5 points of ossification appear: in the upper (membranous) and lower (cartilaginous) parts of the scales, one in the basilar, two in the lateral parts. By the end of this month, the upper and lower parts of the scales grow together, in the 3rd-6th year, the basilar, lateral parts and scales grow together.
Human anatomy S.S. Mikhailov, A.V. Chukbar, A.G. Tsybulkin
The human skull is made up of many small and large bones. For example, there is an occipital bone in its lower back part. She does not have her own pair, but this does not prevent her from creating the wall of the cranium and the cranial vault, as well as the base. If you look at it, you will understand that it is almost perfect, because both the left and right parts are absolutely symmetrical. The occipital bone does not form by itself. It can be considered the result of combining several bones. In many animals, the compound occipital bones can develop separately from each other. From this, it can be assumed that it is created from at least four parts, which finally turn into a single whole only after 3, or even 6 years of life. The closest neighbors of such a complex bone can be considered the parietal, temporal bones, as well as the first cervical vertebra, which has long been officially named Atlas. The part that faces outward has a convex shape, but inside it is noticeably concave. If you turn your gaze to the lower part of the occipital bone, you can see the foramen magnum with the naked eye. It serves as a connection for the cranial cavity and the spinal canal. It can be divided into several parts, or rather four. These are occipital scales, lateral in the amount of two pieces and basilar.
The basilar part of the hike to the quadrangle, but at the same time it is rather short and thick. The back is not burdened by the neighborhood. Perhaps that is why its edge is only slightly sharpened, but you will not see roughness here either. Thus, this part creates a border for the foramen magnum. Now about the front. It also has thickenings, but unlike the back, it is not smooth, but flawed. With the help of it, the body of the sphenoid bone is able to join the occipital part of the skull, and cartilage serves as a connective tissue, which creates sphenoid-occipital synchondrosis. Upon reaching the age of fourteen, this cartilage develops into bone tissue. And the result is a single bone. The upper part is directed towards the cranial cavity. It does not have any roughness, but there is a slight concavity.
The lateral part has a pair. They are located at the back and gradually merge into the scales of the occipital bone. Its lower part is decorated with an ellipsoid eminence or occipital condyle. At its base, a canal was found through which the hypoglossal nerve passes. Going a little back behind the condyle, you can find the jugular notch. Together with another notch, but already the pyramid of the temporal bone, they form the jugular foramen. The jugular notch has a process of the same name. The outer part of it is decorated with a peri-mastoid process. It is in this part that the rectus lateral muscle of the head connects to the occipital part. Literally a millimeter from the jugular notch is the sigmoid cone groove. It is considered part of the temporal bone groove, or rather its continuation. But the smooth jugular tubercle is located almost in the middle.
The occipital bone has scales, which is the integumentary bone. At the same time, it is a plate that is rather convex on the outside and strongly concave on the inside. Outside, the scales are not at all smooth, and one might even say embossed. And all due to the fact that ligaments and even muscles are attached to it. The very center of the outer surface is occupied by the occipital protuberance. You can find it yourself by lightly feeling the skeleton of the head in the back of the head. From this protrusion, the upper nuchal lines diverge on the sides. It is interesting that they do not walk in a straight line, but along a curved one. Slightly above them, but at the same time, parallel to them, you can find the highest nuchal lines. This protrusion was another beginning for the occipital ridge. But you can find its end at the posterior edge of the foramen magnum, and it should be exactly in the middle. From the midline on the crest, the nuchal lines diverge, which run parallel to the upper ones. Thus, the muscles are strengthened. Directly on the occipital bone and ends with the attachment of the muscles with the help of the surface of the occipital scales and the superior nuchal lines. The inner part of the occipital bone completely repeats the pattern of the brain, as well as the shell that protects it. Because of this relief, the bone is divided by two ridges that intersect at right angles. As a result, we get four parts, or, as doctors call them, pits. The protrusion is not only outside, but also inside. You can find it in the brain part of the scales. It is here that the cruciform elevation is located, and already on it is the ledge itself. Several grooves of the transverse sinus originate from the cruciform eminence. The sagittal ridge passes upward, the internal occipital ridge goes down. He, in turn, goes to the posterior semicircle of the foramen magnum.
The occipital bone is prone to injury that can lead to serious consequences. In most cases, if the injury reaches the foramen magnum, it is very likely that the spinal cord will be destroyed, as well as the nerves and blood vessels.
Os occipitale - odd, participates in the formation of the base and roof of the skull. The upper part of the scales of the occipital bone ossifies on the soil of the connective tissue, the remaining parts (main and lateral) - on the soil of the cartilage. The outer surface of the occipital bone is convex, the inner one is concave. The antero-inferior section contains a large occipital foramen, foramen magnum. In the occipital bone, four parts are distinguished: the main, pars basilaris, two lateral parts, partes lateralis, and the occipital scales, squama occipitalis. Up to 3-6 years of a child's life, these parts are separate bones, and then, growing together, they form one bone.
Main part, pars basilaris - short, thick, quadrangular. It limits the large (occipital) foramen, foramen magnum, oval or round (Yu. V. Zadvornov, 1972). The upper surface of the main part is concave in the form of a groove and faces the cranial cavity; it forms a slope, clivus, to which the medulla oblongata is adjacent. In the middle of the lower outer surface there is a small pharyngeal tubercle, tuberculum pharyngeum. The outer, slightly uneven edges of the main part, together with the stony parts, form the stony-occipital fissures, which are filled with cartilage in childhood, and ossify with age.
Side parts, partes lateralis - form the lateral sides of the foramen magnum and connect the main part with the scales. The inner, cerebral surface, at the outer edge, runs a narrow groove of the petrosal sinus, which, together with the same groove of the temporal bone, forms something like a canal where the lower petrosal sinus lies, sul. sinus petrosi inferioris.
On the lower outer surface of each lateral part is the occipital process, condylus occipitalis, for connection with the upper articular surface of the atlas. Behind the occipital condyle there is a condylar fossa, fossa condylaris, with an opening in the bottom that leads into a non-permanent condylar canal, canalis condylaris. On the outer edge of the lateral part, there is a jugular notch, incisura jugularis, on which a small intrasynojugular process, processus jugularis, protrudes. The jugular notch with the notch of the same name on the temporal bone forms the jugular foramen, foramen jugularis, dividing by the intravascular process into the anterior and posterior parts. The jugular vein originates in the anterior, and the cranial nerves pass through the posterior (IX-XI pair). Along the jugular processes on the side of the inner surface of the lateral part, there is a deep groove of the transverse sinus, sul. sinus transversus. In the anterior part of the lateral part, there is a jugular tubercle, tuberculum jugulare, back and down from which, between the jugular and occipital processes, lies the canal of the hyoid nerve, canalis nervi hypoglossi.
Occipital scales, squama occipitalis - has a triangular shape, curved, bounds behind the large occipital foramen. The lateral edge of the scales is divided into two sections: the upper (lambda-like margo lambdoideus) and the lower (mastoid, margo mastoideus). In the middle of the outer surface of the scales is the external occipital protrusion, protuberantia occipitale externa. The upper cervical lines, linea nuchalis supreior, diverge from it to the sides. Above them are additional high cervical lines, linea nuchalis suprema. From the external occipital protrusion down to the large occipital foramen, the external occipital ridge, crista occipitalis externa, is directed. In the middle of the segment connecting the large occipital foramen and the external occipital protrusion, the lower cervical lines, linea nuchalis inferior, diverge in different directions. Muscles are attached to these lines. On the inner surface of the scales is a cruciform eminence, eminentia cruciformis, in which the internal occipital protrusion, protuberantia occipitalis interna, is located. The cruciform eminence divides the inner surface of the scales into four pits, in the lower two are the cerebellar hemispheres, in the upper - the occipital lobes of the brain. From the cruciform eminence, the grooves of the transverse sinus, sul, extend in both directions. sinus transversa - the groove of the superior sagittal sinus goes up, sul. sinus sagittalis superior, and downward - the internal occipital ridge, crista occipitalis interna.
Ossification. The first points of ossification in the occipital bone appear at the beginning of 3 months of prenatal development in the connective tissue and cartilaginous parts. In the cartilaginous part there are five ossification points: one in the main part, two in the lateral parts and two in the cartilaginous part of the scales. In the connective tissue part of the scales, there are two points of ossification. At the end of 3 months, the upper and lower parts of the scales grow together, and the main part, scales and lateral parts grow together at 3-6 years of age. The main part grows together with the body
The occipital bone (os occipitale; Fig. 47, 48) is located in the posterior inferior part of the cerebral skull. Connects with the sphenoid, temporal and parietal bones. Consists of 4 parts located around the foramen magnum.
The basilar part lies anterior to the foramen magnum. In childhood and adolescence, it connects to the body of the sphenoid bone through cartilage, after 18 - 20 years, the bones grow together (synostosis). The upper surface of the basilar part facing into the cranial cavity is smooth, concave; part of the brain stem is located on it. The outer surface is rough, almost in its center the pharyngeal tubercle is visible.
The paired lateral part on its outer surface has elliptical occipital condyles with an articular surface for articulation with the I cervical vertebra. At the base, each condyle is pierced by a sublingual canal. The condyle fossa is visible behind the condyle. On the lateral edge of the lateral part, there is a jugular notch, which, when connected to the notch of the temporal bone of the same name, forms a jugular foramen through which the jugular vein, glossopharyngeal, vagus and accessory nerves pass. A narrow high jugular process protrudes at the posterior edge of the notch, around which an arcuate wide and deep groove of the sigmoid sinus passes. On the upper surface of the lateral part, above the occipital condyle and the hyoid canal, there is a gentle jugular tubercle.
The scales are the most extensive part of the occipital bone. She takes part in the formation of both the base and the roof of the skull. On the inner surface of the occipital scales, there is a cruciform eminence, in the center of which the inner occipital protuberance is visible. Downward from the last to the foramen magnum is the inner occipital ridge. A wide, gentle groove of the transverse sinus is directed horizontally in both directions, and the groove of the superior sagittal sinus is directed vertically upward. The cerebellar hemispheres are adjacent to the wide fossae located below the sulcus of the transverse sinus.
The outer occipital protuberance is visible almost in the center of the outer surface of the scales. The outer occipital crest extends from it to the foramen magnum. There are also horizontal ridges called nasal lines. The upper one is located at the level of the outer ridge, and the lower one is at the level of the middle of the outer ridge.
The sphenoid bone (os sphenoidale; Fig. 49) occupies a central position at the base of the skull. It connects to all bones of the cerebral skull. The bone has a complex shape, outwardly resembles a butterfly, therefore its parts are called accordingly: body, small wings, large wings, pterygoid processes.
The body is compared in shape to a cube and 6 sides are distinguished. The upper side is curved in the shape of a saddle and is called the Turkish saddle. In its center is the pituitary fossa (the lower appendage of the brain, the pituitary gland, is located in it), bounded in front by the tubercle of the saddle, and behind by the back of the saddle. The sphenoid bone is connected by the posterior surface of the body to the basilar part of the occipital bone. On the front surface, two openings are visible leading to the airway of the sphenoid bone. This sinus is formed after 7 years and is located inside the body of the sphenoid bone. The sinus is divided by a septum that extends to the anterior surface in the form of a wedge-shaped ridge. The opener is attached to the lower surface of the body. The lateral surfaces are occupied by small and large wings extending from them.
The small wings are triangular, extend laterally and upward from the body, at the base they are pierced by the optic canal, in which the optic nerve passes. The lower surface of the small wings participates in the formation of the upper wall of the orbit, and the upper surface faces the cranial cavity.
Large wings are directed to the sides. At the base of each of them there are three openings: round in front, then oval and spinous in the area of the wing corner. The branches of the trigeminal nerve pass through the first two, and the artery that feeds the hard shell of the brain passes through the last. The inner, cerebral, surface of the large wings is concave. The convex outer surface is divided into the orbital, which participates in the formation of the walls of the orbit, and the temporal, which is part of the temporal fossa. Small and large wings limit the superior orbital fissure, through which blood vessels and nerves pass into the orbit.
The pterygoid processes are directed downward. Each of them is formed by two plates, which grow together in front, and diverge posteriorly and limit the pterygoid fossa. The medial plate is involved in the formation of the nasal cavity,
ends downward with a pterygoid crochet. The outer surface of the lateral plate faces the infratemporal fossa. At the base, each pterygoid process is pierced from front to back by a narrow pterygoid canal, in which vessels and nerves pass.
The parietal bone (os parietale; Fig. 50) is flat, quadrangular, participates in the formation of the cranial vault. The parietal tubercle is clearly visible on the outer convex surface. The inner, cerebral, surface is smooth, with the usual relief of arterial grooves and depressions from the convolutions of the brain. In the bone, 4 edges are distinguished: frontal, occipital, sagittal, scaly, and, accordingly, 4 angles: occipital, wedge-shaped, frontal and mastoid.
The temporal bone (os temporale; Fig. 51 - 53) is involved in the formation of the base of the skull and its vault. Connects with the sphenoid, occipital and parietal bones. In the temporal bone, three parts are distinguished: stony, tympanic and scaly.
The stony part (pars petrosa), or pyramid, has the appearance of a three-sided pyramid, the top facing anteriorly and medially, and posteriorly and laterally passing into the mastoid process. On the anterior surface, directly at the apex, there is a noticeably wide, gently sloping depression - the trigeminal depression: the trigeminal nerve node is located here. Almost at the base of the pyramid, an arcuate eminence protrudes, due to the upper semicircular canal of the inner ear located under it. The smooth platform of the anterior surface between the arcuate eminence and the scales is called the roof of the tympanic cavity - under it is the tympanic cavity of the middle ear.
On the posterior surface, closer to the middle, the internal auditory opening is clearly visible, continuing into the internal auditory canal. The facial and vestibular cochlear nerves, as well as arteries and veins, pass through it. The outer aperture of the vestibule water supply system is located lateral and downward.
Almost in the center of the rough lower surface is an extensive, deep and smooth jugular fossa, and in front of it is the external opening of the carotid canal. Lateral to the jugular fossa, there is a long, sharp styloid process going down and anteriorly - the place where several muscles and ligaments begin. At its base there is a styloid opening through which the facial nerve leaves the skull.
The base of the stony part is massive, expanded, passes into the mastoid process, to which the sternocleidomastoid muscle is attached. The mastoid process is bounded by the mastoid notch. On the inner, cerebral, side of the mastoid process, a wide groove of the sigmoid sinus runs in an arcuate manner, from which the mastoid opening, a non-permanent venous graduate, leads to the outer surface of the skull. Inside, the mastoid process contains air cells that communicate with the middle ear cavity through the mastoid cave.
The scaly part looks like an oval, upright plate. On the inner, cerebral, surface, imprints of the convolutions of the brain and arteries are noticeable. The outer temporal surface is smooth, takes part in the formation of the temporal fossa. Anterior to the external auditory meatus from the scaly part, the zygomatic process departs first laterally, and then forward, forming part of the zygomatic arch. At the base of the process, on the temporal surface of the scaly part, there is a mandibular fossa for articulation with the lower jaw. In front, it is limited by the articular tubercle.
The tympanic part in the form of a thin plate limits the front, bottom and back of the external auditory opening and the external auditory canal; grows together with the mastoid process and the scaly part.
Several canals pass inside the temporal bone (see Fig. 53). 1. The facial canal contains the facial nerve. It begins in the internal auditory canal, goes horizontally forward to the middle of the anterior surface of the pyramid, then turns almost at a right angle to the lateral side, at the medial wall of the tympanic cavity it goes vertically downward and ends with the styloid foramen. 2. The sleep canal begins on the lower surface of the pyramid with an external opening. First it goes vertically upward, then bends smoothly, changes its direction to horizontal and emerges at the top of the pyramid. The internal carotid artery runs inside the canal. 3. The musculocutaneous canal opens with a hole in the corner between the anterior end of the pyramid and the scales of the occipital bone, and ends in the tympanic cavity. The septum is divided into two half-channels: the half-channel of the muscle straining the eardrum, and the half-channel of the auditory tube, through which the middle ear cavity communicates directly with the pharyngeal cavity.
The temporal bone contains a complex organ of hearing and balance: part of the external auditory canal, middle and inner ear. The internal carotid artery, the facial nerve, the vestibular cochlear nerve, the branches of the lingopharyngeal and vagus nerves, the trigeminal nerve node, and part of the sigmoid venous sinus are also located here.
The frontal bone (os frontale; Fig. 54) takes part in the formation of the fornix and base of the skull, orbit, nasal cavity and temporal fossa. From the bones of the cerebral skull it connects with the ethmoid, wedge-shaped and parietal. 4 parts are distinguished in it: frontal scales, paired orbital and nasal.
The frontal scales are flat, directed vertically and posteriorly. Its outer surface is convex, smooth; almost in the center of this surface are the frontal tubercles. From below, the frontal scales ends in a sharp supraorbital edge, in the medial section of which the supraorbital notch (supraorbital foramen) for the vessels and nerve of the same name is visible. Laterally, the supraorbital margin ends with a sharp zygomatic process, to which the zygomatic bone is attached. The temporal line running posteriorly and upward from the zygomatic process separates the temporal surface from the common outer surface of the frontal scales, which participates in the formation of the temporal fossa. Above the medial part of the supraorbital margin, the superciliary arches are visible, above which there is a flat, smooth platform - the glabella, or glabella. On the inner concave side of the frontal scale, depressions from the convolutions of the brain and arteries, as well as the groove of the superior sagittal sinus, are noticeable.
The paired orbital part has the form of a horizontally located triangular plate. The lower, orbital, surface is smooth, concave, forms most of the upper wall of the orbit. Near the zygomatic process, there is a fossa of the lacrimal gland on it, and in the anteromedial section there is a block fossa (with a block spine). The superior, cerebral, orbital surface is convex, has a characteristic cerebral relief.
The horseshoe-shaped nose surrounds the trellised notch. Pits for articulation with ethmoid cells are visible on it. In the thickness of the bone is the airway frontal sinus.
Ethmoid bone (os ethmoidale; Fig. 55) takes part in the formation of the base of the skull, nasal cavity and orbit. Its horizontal lattice plate enters the lattice notch of the frontal bone. Lattice labyrinths with lattice cells hang on the sides of the horizontal plate. The upper and middle turbinates are located on the inner surface of the labyrinth. The perpendicular plate is involved in the formation of the septum of the nasal cavity. At the top, it ends with a cock's comb.
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